TM 1-1500-204-23-9(d)Oil and water accumulation. Openthe siphon valve and drain accumulated water and oilfrom receiver.(7)Maintenance.Consult the applicablemaintenance manual for scheduled and preventivemaintenance requirements.h.AircraftPreheater.The aircraft preheater,shown in figure 9-15, will deliver 40,000 to 400,000BTUs/hour within the specified operating conditionlimits. The preheater will deliver uncontaminated airwith a regulated discharge air temperature of 150 to280°F (66 to 138C)at an adjustable air delivery rate of435 to 815 cfm. Flexible ducts are used to direct theheated air where it is needed.(1)Purpose.The aircraft preheater isspecifically designed to preheat aircraft engines,cockpits and cabins when the aircraft is in cold weatherareas. It is often used to provide heat to aircraftrepairers as they perform outdoor maintenance in thewinter.(2)Principles of operation. The aircraftpreheater has a prime mover assembly and a heatgenerator assembly.(a)Prime mover assembly. The primemover is either a gas engine or an electric motor whichdrives afan, a fuel pump, and a magneto. The fanmoves the air to be heated through the heat exchangersection of the heat generator and also supplies the airfor combustion. The fuel pump supplies fuel forcombustion in the heat generator and to run the gasengine. The magneto ignites the combustion fuel andair mixture in the combustion portion of the heatgenerator.(b)Heat generator assembly.Throughthe medium of a heat exchanger, the heat generatorheats the inlet air with hot gases generated by fuelburned in the combustor. The air and exhaust flow areso arranged that there can be no intermingling ofexhaust gases with the heated air.(3)Safety practices and procedures.Thefollowing special precautions should be observed whenusing the aircraft preheater:· Do not use inside a structure due to possiblecarbon monoxide poisoning. Park the preheateroutside and run ducting to the inside.· Periodically look for leaks in the fuel system.· Locate the unit so that the exhaust does notblow into the inlet door.· Let the unit cool down before refueling.· Be sure the exhaust stack extension is in place.· Ensure all outlet and inlet access doors areopen.(4)Operating procedures.Consult theapplicable maintenance manual for detailed instructions.The following general procedures pertain to theoperation of the aircraft preheater:(a)Position the preheater so that thewind blows the exhaust away from the air inlet opening.(b)Open the air inlet canopy door, airoutlet doors, access doors, and the exhaust stack door.(c)Connect the flexible duct andposition it as needed.(d)If using the gas engine primemover, start the engine. If using the electric motorprime mover, plug it in to a power source, normally 115vac, and turn switch on.(e)Regulate the heat by using thetemperature selector valve.(f)To stop the preheater, pull theburner fuel knob to stop the combustor fire. Allow theprime mover to run for about 2 minutes for coolingpurposes.(g)Stop the prime mover by pressingthe stop switch button on the gas engine or by turningthe switch on the electric motor to off.(5)Inspection.The operator should performthe following general inspections before using theaircraft preheater. Detailed inspection requirements arefound in the applicable maintenance manual.(a)Gas tank.Check the level and refillas necessary.9-42